Bump, because after updating to windows 10 2004 (may update) i started experiencing the same issue. I usually have 165hz on a gsync monitor. Now it is capped at 60~65fps for no reason. Nothing I did could fix it.
And warframe is the only game where I experience this issue. I also play Forza Horizon 4 where I got a major increase in FPS (80~100 to 120-140). Where did things go wrong?
Thing I've tried: Changing compatibility settings, double checking nVidia control panel settings. Checking game mode whether there's a difference while disabled (none). Reinstalling my nVidia drivers.
I don't know what else to do frankly, besides rolling back. I find it silly however to do a rollback to the previous version while it is in fact one of the most stable updates Microsoft has pushed so far, looking back at their previous updates this past half year that just broke the OS. I hope this gets attention soon.